JPH0240889B2 - - Google Patents

Abstract

PURPOSE:To prevent a change of fluid pressure in a pressure fluid chamber, by providing an inner piston, which is adapted to a brake pad, to be arranged through an elastic material in the inside of a piston in a caliper body. CONSTITUTION:A disc brake device 10 slidably supports a caliper body 13 through a sliding pin 12 to a bracket 11. The caliper body 13, which is placed across a brake disc 17, integrally rotating with a wheel, by a bridged part 16, provides brake pads 18, 19 to be mounted. A working part 14 forms a cylinder 20 here fitting a bottomed cylindrical outer piston 21 to be inserted. An inner piston 23 is provided inside the outer piston 21, and a damper member 25 of elastic material of rubber or the like exists interposing between the inner piston and the internal periphery of a cylindrical part 21d of the outer piston 21. In this way, load distribution of the brake pad 18 is uniformly obtained, while deflection of the disc 17 is absorbed by the damper member.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a disc brake device, and more particularly to a disc brake device equipped with a double-structured piston.

[Conventional technology]

With disc brakes, so-called squealing phenomenon may occur during braking. One of the reasons for this is that during braking, the end of the brake pad on the brake disc retraction side is pressed more strongly against the brake pad than the rest of the pad, resulting in high frequency vibrations and noise called the so-called squeal phenomenon.

Therefore, as a device for reducing this squealing phenomenon, there is a disc brake device equipped with a double-structured piston, as disclosed in, for example, Japanese Patent Publication No. 51-39311.

As shown in FIG. 5, cylinder holes 3, 3 are formed opposite to a caliper body 2, which is disposed straddling a brake disc 1 that rotates together with a wheel (not shown). A hydraulic chamber 6 is defined between the bottom of the piston 4 and the bottom of the cylinder hole 3 by inserting bottomed cylindrical pistons 4, 4 into the cylinder holes 3, 3, respectively, with the opening side of the piston 4 facing toward the brake pads 5, 5. A pad pushing member 8 in which a number of plates are arranged in the radial direction of the brake disc 1 is disposed inside the piston 4 via an annular positioning member 7 made of rubber or the like, and a pad pushing member 8 protrudes from the piston 4. 8
One end of the pad is brought into contact with the back plate 5a of the brake pad 5 to equalize the load distribution on the pad and reduce the so-called squealing phenomenon during braking.

However, in addition to the above reasons, the so-called squealing phenomenon is caused by vibration of the brake disc, uneven wall thickness, etc., which prevents the entire surface of the brake pad from being pressed against the brake disc evenly, and fluctuations in this pressing force cause the fluid in the hydraulic pressure chamber to This results in pressure fluctuations and torque fluctuations, and these vibrations are transmitted to the vehicle body, undercarriage, steering wheel, etc., resulting in a squealing phenomenon and also causing abnormal vibrations during braking.

[Problem that the invention seeks to solve]

However, in the disc brake with the above structure, the other end of the pad pushing member is in surface contact with the piston, so the tilting of the pad pushing member is transmitted to the piston, causing the piston to displace, causing fluid pressure fluctuations and torque fluctuations. occurs.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a disc brake device that eliminates radial displacement of a piston, prevents fluid pressure fluctuations and torque fluctuations in a hydraulic pressure chamber, and reduces the occurrence of vibrations.

[Means for solving problems]

In order to achieve the above object, the present invention includes a bottomed cylindrical piston that is fluid-tightly and movably inserted into a cylinder hole formed in a caliper body, with the opening end facing toward the brake pad side, and the bottom of the piston and the cylinder hole In a disc brake device that defines a hydraulic chamber between the bottoms of the piston, inside the piston,
A bottomed cylindrical inner piston having an open end protruding from the opening of the piston and a flange having an enlarged diameter formed at the open end is fitted, and an axis on the outside of the bottom of the inner piston is inserted into the inner piston. Flange portions formed to expand in diameter at the open end of the inner piston are brought into contact with the brake pads on the axis inside the bottom of the piston, and an elastic material is interposed between the inner piston and the piston. It is characterized by

[Effect]

As a result, during braking, the inner piston pushes the brake pad, and the displacement of the inner piston is absorbed between the inner piston and the piston and is not transmitted to the piston, thus preventing fluid pressure fluctuations in the fluid pressure chamber from occurring. Furthermore, the occurrence of torque fluctuations is also prevented. In addition, a flange with an expanding diameter is formed at the open end of the inner piston, and this flange is brought into contact with the brake pads, so the load applied to the brake pads during braking is evenly distributed and the brake pads do not warp. There is no risk and uneven wear will not occur.

〔Example〕

Embodiments of the present invention will be described below with reference to FIGS. 1 to 4.

FIGS. 1 and 2 show a first embodiment of the present invention, in which a disc brake device 10 is capable of sliding a caliper body 13 on a bracket 11 fixed to a vehicle body via sliding pins 12, 12. The carrier body 13 integrally connects the actuating part 14 and the reaction force part 15 with a bridge part 16, and straddles the brake disc 17 which rotates together with the wheel at the bridge part 16. Brake pads 18 and 19 are provided on both sides of the brake disc 17, with an actuating part 14 and a reaction part 15 arranged on both sides, and which pinch the brake disc 17.
is attached.

A cylinder 20 is formed in the operating portion 14, and a bottomed cylindrical outer piston 21 is fitted into the cylinder 20 in a fluid-tight and movable manner.
The outer piston 21 is fitted into the cylinder 20 with the opening 21a facing the back plate 18a of the brake pad 18, and defines a hydraulic chamber 22 between the bottom 21b and the bottom 20a of the cylinder 20.

This outer piston 21 is provided with an inner piston 23 inside thereof. The inner piston 23 has a cylindrical shape with a bottom, and is a steel ball disposed between a recess 23b formed in the axis of the bottom 23a and a recess 21c formed in the inner axis of the bottom 21b of the outer piston 21. 24,
A damper member 25 made of an elastic material such as rubber is interposed between the outer periphery of the cylindrical portion 23c and the inner periphery of the cylindrical portion 21d of the outer piston 21, and the opening end 23d protrudes from the opening 21a of the outer piston 21. The flange 23e formed to expand in diameter is attached to the brake pad 1.
It is in contact with the back plate 18a of No.8.

With this configuration, the load distribution on the brake pads 18 is equalized during braking, and
Even if displacement occurs in the inner piston 23 due to vibration of the brake disc 17 or uneven wall thickness, the displacement is absorbed by the damper material 25 and the outer piston 21
Since the outer piston 21 is not displaced in the radial direction, the outer piston 21 moves within the cylinder 20 without twisting, and therefore, no fluid pressure fluctuation occurs in the fluid pressure chamber 22. Vibrations are prevented, so-called squealing phenomena and abnormal vibrations during braking are reduced.

Further, FIG. 3 shows a second embodiment of the present invention, in which a piston 30 fitted into a cylinder 20 is integrated by sandwiching a steel ball 24 and an oil-impregnated sponge 33 between an outer piston 31 and an inner piston 32. Similarly to the previous embodiment, the displacement of the inner piston 32 is absorbed by the oil-impregnated sponge 33 and is not transmitted to the outer piston 31.

Furthermore, FIG. 4 shows a third embodiment of the present invention,
A contact portion 35b that protrudes inward of the outer piston 35 is integrally formed on the axis of the bottom portion 35a of the outer piston 35 that is inserted into the cylinder 20, and the axis of the inner piston 23 is brought into contact with this contact portion 35b, A damper material 36 is interposed between the open end 35c of the outer piston 35 and the outer periphery of the open end 23e of the inner piston 23, so that the displacement of the inner piston 23 is absorbed by the damper material 36 and transferred to the outer piston 35. Not communicated.

Note that the contact portion may be provided on the inner piston side, or may be provided on both the inner piston and the outer piston.

〔Effect of the invention〕

As described above, the present invention includes forming, on the inside of a bottomed cylindrical piston fitted into a cylinder of a carrier body, a flange portion having an open end protruding from the opening of the piston and having an enlarged diameter at the open end. A flange portion into which a bottomed cylindrical inner piston is fitted, and the flange is formed so that the axis on the outside of the bottom of the inner piston is aligned with the axis on the inside of the bottom of the piston, and the diameter expands to the open end of the inner piston. are brought into contact with the brake pads, and an elastic material is interposed between the inner piston and the piston, so that the load distribution on the brake pads is equalized during braking,
In addition, even if displacement occurs in the inner piston due to brake disc vibration or uneven wall thickness, the displacement is absorbed by the elastic material and not transmitted to the outer piston, and no fluid pressure fluctuation occurs in the hydraulic pressure chamber. Vibrations are prevented, so-called squealing phenomena and abnormal vibrations during braking are reduced. In particular, by making the flange, which is formed to expand in diameter at the open end of the inner piston, come into contact with the brake pads, the load applied to the brake pads during braking is evenly distributed and concentrated only in the center of the brake pads. Therefore, there is no risk of warping of the brake pads, and uneven wear will not occur.

[Brief explanation of drawings]

1 and 2 show a first embodiment of the present invention, FIG. 1 is a plan view of a disc brake device, FIG. 2 is a sectional view taken from FIG. 1, and FIG. 3 is a second embodiment of the present invention. A sectional view showing the embodiment, FIG. 4 is the third embodiment of the present invention.
A sectional view showing the embodiment, and FIG. 5 is a sectional view showing a conventional example. 10... Disc brake device, 13... Caliper body, 17... Brake disc, 18,
19... Brake pad, 20... Cylinder, 2
1, 31, 35... Outer piston, 22... Hydraulic pressure chamber, 23, 32... Inner piston, 25, 3
6...damper material, 33...oil-impregnated sponge.

Claims (1)

[Claims] 1. A cylindrical piston with a bottom is fluid-tightly and movably inserted into a cylinder hole formed in the caliper body with the open end facing toward the brake pad, and a hydraulic chamber is formed between the bottom of the piston and the bottom of the cylinder hole. In the disc brake device, a bottomed cylindrical inner piston having an open end protruding from the opening of the piston and a flange whose diameter increases is inserted into the inner side of the piston. At the same time, the axis of the outer side of the bottom of the inner piston is brought into contact with the axis of the inner side of the bottom of the piston, and the flange portion formed to have an enlarged diameter at the open end of the inner piston is brought into contact with the brake pad, and A disc brake device characterized in that an elastic material is interposed between an inner piston and the piston.